The Dominion Observatory is carrying out a program to investigate the direction of faulting in large earthquakes through the study of first motion at distant stations. In this, the third paper of the series, solutions are obtained for fifteen earthquakes, with focal depths varying down to 600 km. For the first time, data from PP and P′ are used in obtaining solutions.
Seven of the earthquakes considered lie in the North Pacific Ocean, four in South America, two in the southwest Pacific and two in central Asia. The two earthquakes in central Asia apparently occurred on steeply dipping normal faults, but most of the circum-Pacific shocks are due to transcurrent faulting.
No attempt is made to correlate the results with structure. The attempt will be postponed until more earthquakes have been reduced.